Anjum Muneer Raja, 40, was returning home on a motorcycle late on Thursday night when the bike-borne attackers waylaid him and opened fire, the police said.
The incident had occurred on the Bank Road, minutes away from the Pakistani military's national headquarters, the Dawn News reported.
Raja was shot six times on the head, neck and torso, killing him instantly, the report said, adding the attackers then fled
Raja was father to a five-year-old boy and used to teach at a school in the mornings and worked as a sub-editor for a Islamabad-based Urdu newspaper in the evenings, his uncle Tariq Mehmood said.
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The journalist community condemned Raja's murder and demanded immediate arrest of the attackers. The scribes have also demanded protection for all journalists and threatened protest if Raja's killers are not held soon, the report said.
Last year prominent reporter Ahmed Noorani was also savagely beaten and stabbed in the head after being dragged out of his car in Islamabad by armed assailants.
Pakistan is among the most dangerous countries in the world for journalism, France-based watchdog Reporters Without Borders (RSF) said in its annual press freedom report last May.
At least 117 journalists have been killed in the past 15 years in Pakistan, and of these, only three cases were taken up in the judicial courts.